Stabilized cellulose acetate



Patented Nov. 30, 1948 STABILIZED CELLULOSE ACETATE William John Simpsonand Donald Finlayson,

Spondon, near Derby, England, assignors'to Celanese Corporation ofAmerica, a corporation of Delaware No Drawing. Application August 6,1946, Serial No. 688,706. In Great Britain August 21, 1945 fibres, foilsand films, and is an improvement in or modification of the invention ofU. S. application S. No. 510,787, filed November 18, 1943 (Patent No.2,432,517).

As is stated in the parent specification, when fibres, foils and similarproducts having a basis of cellulose acetate or other cellulose ester orether are exposed for a substantial period to the action of ultra-violetlight, they undergo, in general and in company with fibres, foils andthe like of other materials (e. g. fibres of cotton or regeneratedcellulose) a marked loss of tensile strength. This latter is usuallyaccompanied by a reduction in the intrinsic viscosity of the material ofthe fibres, foils and the like.

According to the parent specification, this undesirable action ofultra-violet light on cellulose acetate or other cellulose ester orether, or compositions having a basis of such esters or ethers,(including articles formed of such esters or ethers or compositions), isvery greatly reduced by including in the cellulose ester or ether orcompositions a proportion, not exceeding 15% based on the weight of thecellulose ester or ether, of an ester of low volatility of an aromatichydroxy carboxylic acid with a phenol, an alcohol containing an aromaticnucleus, or a cycloaliphatic alcohol. Good results are obtained withfrom 1% to 10%, e. g. By the term low volatility is meant that the esterdoes not lose more than 5% by weight when one gram thereof is heated ina dish in air at 60-70 for 20 hours.

According to the present invention, the esters used to reduce thedestructive action of ultraviolet light contain in their molecules theresidues of two or more molecules of aromatic hydroxy carboxylic acid.An especially important series of compounds are the esters of diorpoly-phenols with aromatic hydroxy carboxylic acids.

The residue of the aromatic hydroxy carboxylic acids employed in theesters of the present invention are preferably those of hydroxy benzene0r hydroxy naphthalene monocarboxylic acids, for example salicylic acid,para-hydroxy-benzoic acid, para-cresctinic acid,2-hydroxy-naphthalene-3-carboxylic acid andl-hydroxy-naphthalene-Z-carboxylic acid. Specific compounds for useaccording to the present invention include salicoyl-salicylic acidphenyl ester, tetra-salicylic acid methyl ester, (in which compounds thehydroxy group of one molecule of an aromatic 4 Claims. (Cl. 106-182)hydroxy-carboxylic acid is esterified with another molecule of anaromatic hydroxy-carboxylic acid) and, among the preferred bodies,resorcinol disalicylate, hydroquinone disalicylate,B-naphthohydroquinone disalicylate, resorcinol dipara-cresotinate,hydroquinone di-para-cresotinate, and'the di(2:3-oxynaphthoic) -ester ofresorcinol.

- As in the parent specification, good results are obtained using from 1to 10%, e. g. 5% of the substance based on the: cellulose acetate orother cellulose derivativej For example, a'film (0.003 inch thick) ofcellulose acetate containing about 5% of resoroinol disalicylate on theweight of the cellulose acetate suffers, on exposure to light from amercury lamp, a percentage loss in strength only about one-eighth ofthat of 'a similar film free from the salicylate. The other bodiesincluded within the present invention have a similar effectiveness asregards maintenance of strength. Moreover, the bodies are of lowvolatility and are substantially retained in the material and remaineffective during normal storage and use of the cellulose ester or etherproducts. Under the action of ultra-violet light, the materials remainsubstantially colourless, and further, when subjected to bending tests,they do not exhibit brittleness.

The new compositions can, as indicated above, be in the form of fibres,foils, films or other shaped articles.

The incorporation of the ester of the aromatic carboxylic acid with thecellulose ester or ether can be effected in various ways, for example inany of the ways used for incorporating plasticiseifs with celluloseesters or ethers. Thus the cell lose ester or ether and the ester of anaromat c carboxylic acid can be dissolved in a commdn volatile solvent.For instance, in the case of cellulose acetate, acetone may be used or amix ture of acetone with diacetone alcohol. The solutions so obtainedcan then be spun into fibres, e. g. by dry spinning methods, or castinto foils or films and the solvent evaporated, or used as a lacquer forthe production of coatings on textiles, wood, metal, or other materials.Again the cellulose ester or ether, for example as textile fibres,whether loose fibres or in the form of yarns or fabrics, may be allowedto absorb the ester of the aromatic carboxylic acid from an aqueousdispersion of the latter or may be impregnated with a solution of theester of the aromatic carboxylic acid in a liquid which is not a solventfor the cellulose ester or ether, but advantageously is a swelling agenttherefor, and the liquid then evaporated. For instance the ester can beincorporated in cellulose acetate textile material by impregnating thelatter with a solution of the ester in aqueous ethyl alcohol, forinstance aqueous ethyl alcohol of '70 to 90% strength by weight, e. g.ethyl alcohol in the form of methylated spirit. Solutions in aqueouspropyl or isopropyl alcohol can likewise be employed.

Plasticizers may be incorporated in the compositions according to theprecise properties it is desired to impart thereto. Again still othermate rials may be included therein, for example filling materials orcolouring matters. v

The cellulose derivative of the compositions can be cellulose acetate asmentioned above. Again it can be'cellulose propionate, butyrate, oracetate-butyrate, or a cellulose ether, for'instance ethyl or benzylcellulose.

The invention is illustrated by the following example.

Example A cellulose acetate dope of the following composition isprepared:

Resorcinol disalicylate gms' 0.75 Cellulose acetate gms 15.0 Diacetonealcohol ccs' 10.0 Acetone ccs 90.0

This dope is then cast on. a film casting surface of metal or glass andthe volatile solvent evapo- K rated so that a film of from 0.001 to0.003 inch in thickness is obtained. The films so-producedlose verylittle tensile strength when exposed to ultraviolet light from aquartz'mercury vapour lamp under conditions which reduce by 90% thetensile strength of a filmprepared in a similar manner but without theresorcinol disalicylate. The films from the group consisting of benzenenuclei and naphthalene nuclei.

2. A composition of matter consisting essentially of cellulose acetateand, to reduce the destructive action of ultra violet light on thecellulose acetate, from l10% of resorcinol disalicylate.

3. Cellulose acetate fibers containing from 1- 10% of resorcinoldisalicylate based on the weight of the cellulose acetate.

4. Cellulose acetate films containing from 1- 10% of resorcinoldisal'icylate based on the weight of the cellulose acetate.

WILLIAM JOHN SIMPSON. DONALD FINLAYSON.

REFERENCES CITED- The following references are of record in the fileofthis patent:

UNITED STATES PATENTS Number Name Date 1,193,178 Mork Aug. 1, 19161,319,229 Lindsay Oct. 21, 1919 2,086,418 Hunt July 6, 1937 Britton Jan.8, 1946

